Heretofore, negative-working lithographic printing plate precursors have been widely known and various kinds of photosensitive layers (image-recording layers) have also been known. The photosensitive layers include, for example, a diazo resin-containing type, a photopolymerization type and a photo-crosslinking type. In order to prepare a lithographic printing plate, it is ordinarily conducted that a transparent negative original (a lith film) is placed on such a lithographic printing plate precursor and the lithographic printing plate precursor was exposed imagewise using an ultraviolet ray. However, such operations require a great deal of time and effort. In recent years, with the progress of image-forming techniques, a computer-to-plate technique has been developed wherein the plate-making is conducted by laser exposure based on digitized image data, for example, a computer, directly to the lithographic printing plate precursor, without using a lith film. Lithographic printing plate precursors of high-sensitive laser recording system used for the technique have also been developed.
For the photosensitive layer used in the lithographic printing plate precursor of laser recording system, the photopolymerization type is most suitable from the standpoint of high-sensitivity. However, since adhesion of the sensitive layer of photopolymerization type (photopolymerizable layer) to a support is not necessarily strong, disadvantages occur in that a solid image portion fails and that a fine line or a highlight portion becomes thin or drops out, when a lithographic printing plate prepared therefrom is subjected to printing of high-speed and a large volume. Therefore, the adhesion between the photosensitive layer and the support is an important factor in the lithographic printing plate precursor of high-sensitive photopolymerization type, and a large number of investigations and developments have been made.
For instance, it is known to provide a polymer containing a polymerizable group having an ethylenically unsaturated bond and a phosphoric acid group between a photosensitive layer of polymerization type and a support (refer to JP-A-2-304441 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)). Also, techniques are known wherein a functional group capable of causing an addition reaction with a radical is provided on a surface of support by a covalent bond to impart adhesion to a photosensitive layer of photopolymerization type (refer to JP-A-3-56177, JP-A-7-159838 and JP-A-8-320551).
Further, it is also known to provide a layer containing a compound prepared by hydrolysis and dehydration condensation of a silane coupling agent having an ethylenic double bond and a compound having an alkyleneoxide chain and an acryloyl group or a methacryloyl group in its molecule between a photosensitive layer and a support (refer to JP-A-10-282679).
Moreover, a technique of incorporating a phosphoric ester compound having a (meth)acryloyl group into a photosensitive layer to improve adhesion to a support is known (refer to JP-A-11-30858).